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					                                   MSW Composting Report REV 2.0

                    MSW COMPOSTING:

                            William F. Brinton, Richard B. Brinton
                                Woods End Research Laboratory
                                Mt Vernon USA — Stroud UK

1. Summary
The composting of municipal solid waste (MSW) is among the oldest of the large-scale compost-
ing methods. Originating in the mid 40’s and post-war years, MSW compost plants of European
design spread world-wide and reached a peak in the late 60’s. Following this era, there has been a
steady decline in such plants, and presently there are only one-half the number that were found at
the beginning of the 70’s.
The explanation of the decline in traditional MSW composting is twofold: 1) a gradual loss of
confidence in the marketplace as a result of poor product appearance, and 2) unacceptable con-
centrations of contaminants when compared to composts deriving from source-separated materi-
Recent surveys indicate that European mixed-MSW composts often fail to meet EEC metal and
contaminant standards. For these reasons, countries including Germany, Austria, Holland, Swit-
zerland and France have terminated or are in process of converting existing mixed MSW plants.
By 1994, Holland requires that all trash be collected and handled in fully separated form.
German studies show metal (Pb, Cd) content of MSW composts to be approximately 8-x higher
than comparison bio-composts. Similar studies show that organic hydrocarbon contaminants in
MSW composts are 5-x, 3-x and 9-x higher than bio-composts for PCB, polycyclic-aromatic
hydrocarbons (PAH) and dibenzo-Dioxins/Furans (PCDD/F), respectively. Comparison studies
indicate that PAH’s are significantly higher in urban collection but PCB and PCDD/F levels are
similar between urban and rural MSW collection sources. The fine fraction of MSW composts
contains the highest levels of the contaminants making separation by physical sieving very diffi-
Preliminary findings for ``Bio-waste’’ collection/composting systems (household organics + yard
debris) which have been launched throughout central Europe demonstrate that composts can be

   1. Based on a revised lecture presented at Washington State University, Dec 10, 1992

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achieved which are very low in contaminants and meet the new stringent EEC standards, which
are close to background soil levels. Market confidence is expected to to increase with the imple-
mentation of source-separate-only compost technologies. The adoption of similar practices in the
United States is likely to result in wide acceptance among composters and consumers.
2. Introduction
The current emphasis on solid waste reduction via composting overshadows the fact that compost
markets lie primarily in the retail consumer arena, where quality determinants often rank equal to
price [Kupel, 1988, Derr, 1980]. In Europe, where large amounts of composts are produced and
distributed, a recent survey of has revealed that of the end use, 30% is represented by gardeneres,
29% by landscapers, while 10% goes to bulk agricultural markets and 1% to vineyards [Turk and
Fricke, 1992]. Appreciation of the structure of compost markets is one of the forces that has
brought about a shuffeling of priorties in MSW composting [Poletschny, 1993]. This report is
based on an evaluation of issues and research findings arising chiefly out of current European
efforts [Brinton, 1992].
2.1 Background Information to MSW Composting
It was general practice in Europe up until the 1970's, that municipal composts were made from
the mixed municipal solid waste stream (MSW compost), with some larger mixed-MSW plants in
operation since the 1950's [Hangen, 1991]. In America, the trend of mixed MSW composting is
more recent, although descriptions of early attempts at mixed waste composting can be found
[Pfeiffer, 1953]. In Europe, in the early 1970's, both the agricultural community and general pub-
lic starting becoming more concerned about contaminants and in particular heavy metals in soil
and foods. With the findings that many of the higher metal levels were associated with MSW-
compost and sewage sludge applications, the use of composts was reduced if not halted altogether
. Significant marketing difficulties arose for MSW compost products. Compounding the difficul-
ties facing the MSW composts were the generally high level of foreign material it often contained
(glass, plastic, metals) as well as other organic chemical contaminants, such as PCBs, PCPs and
dioxins [Harms, 1982, 1983]. The net effect was that composts fell into a period of disrepute
amongst many gardeners and farmers, and by the mid 1970's a significant downward trend in
sales was apparent [Kassel, 1992; Hangen, 1991; Kraus, 1992].
During the late 70’s and through the 80’s an extensive amount of research was performed in
Europe and particulary in Germany in the field of compost contaminants. As a result of these
studies, a new trend in composting efforts was evident by the mid to late 1980's resulting in a
complete reshift of composting practices away from MSW to the composting of source separated
organic wastes. Currently there are only four MSW composting plants left in Germany, and three

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of these are being decommissioned in the near future [Wiemer, 1992]. Similarly, MSW plants
which were once numerous in France, Austria and Switzerland have been closed or re-designed
for the new Bio-Waste composting programs. In view of these facts, recent emphasis in the
United States on mixed-MSW composting is surprising [SWCC, 1991].
2.2 New Perspectives and Terminology for Source Separated Wastes
The change in point of view on acceptability of separation technologies and composting methods
has occassioned a rise of new terminolgy. Distinct differences in American vs European perspec-
tives are now apparent in the expressions used. There is no longer an equivalent expression for the
American term “MSW” in Europe. Ultimately, all waste once properly identified and sorted, will
carry a specific rather than general name as implied in MSW.
Europeans have developed a terminology for different types of composts and wastes. ‘Bio-wastes’
(Bioabfall) include separated yard and residential food wastes; thus, ‘Bio-waste composts’ are
those made from these materials. ‘Green-waste composts’ are those made only from green
wastes, or, as referred to in the USA, yard wastes. ‘Wet waste composts’, resulting from the basic
twofold separation of wet and dry wastes, are not considered to be ‘source separated’. In fact, wet
waste compost programs in Europe are going the way of mixed MSW composting, since scientific
tests indicate little if any reduction in contaminant levels in the final composts.
While bio-waste composts in the European view may contain food wastes from the food industry,
paper wastes are not generally allowed in this category, due primarily to the levels of heavy metal
contaminants. Presently, an additional category is being discussed which would include bio-waste
plus paper as a result of recognition that paper may be a valuable addition to compost source
materials. This may have particular application for industrial paper wastes.
A series of studies were launched in Europe with Procter and Gamble support to test inclusion of
diapers in Bio-waste collection programs. Two German and one Swiss study reached similar con-
clusions. The high content of zinc in diaper materials from zinc-oxide baby creams pushed tests
composts close to and in some cases over the acceptable threshold level for zinc. Pathogen reduc-
tion from fecal matter was concluded in one study to be sufficient provided the composting oper-
ation was well run. The result of these studies on public policy was not favorable. German, Swiss
and Austrian authorities adopted rules essentially banning diapers from Biowaste programs.[Kas-
sel, 1991]
With new European regulations on paper waste and recycling specifying limits for metal levels in
printed matter, it is conceivable that in the not too distant future household paper waste will be
permitted in the bio-bins [Fricke et al, 1991].
As a summary, early MSW composting emphasis in Europe led to numerous studies which

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reached conclusions favcoring a high level of source separation prior to composting;
• waste fractions should be kept as much as possible in forms in which they are best usable;
• the uneccessary mixing of diverse waste materials is to be reduced as much as possible in order
  to cut-down contamination in the environment;
• harmful or hazardous compounds are to be treated in the most appropriate and effective manner,
  and not through composting.

3. Source-Separated Compost Participation in Germany
Hessen was the earliest German state to launch source separated bio-waste composting. This state
presently has the most extensive participation. Many regions and municipalities have begun simi-
lar separate biowaste composting programs. The most extensive survey of bio-waste composting
in Germany was carried out by Fricke et al [Fricke, 1991].The following table gives statistics on
source separated bio-waste composting in Germany.
The figures cited are generally those for curb-side collection systems (including yard wastes), and
do not fully account for materials coming from food industry sources which contribute directly to
composting sites. The figures also do not take into account home-composted kitchen and yard
wastes, nor do they include farm composted animal manures [Jung]. Therefore, the totals for com-
posted wastes are most likely conservative estimates and could be as much as 30-50% higher, if
all forms of residential and community composting were accounted for [Fricke, 1991].

 Table 1: Current Source Separated (Bio-waste) Collection and Composting Programs in
                     the Federal Republic of Germany (Old States)
 GERMAN STATE                                              CURRENT (Aug 1991)
                                   Residents      Per-      Bio-waste       Sites    Bio-waste        Compost
                                    served        cent     per resident               quantity        Quantity
                                                  (%)      (avg. kg/yr)               (t/yr) *         (t/yr) *
 Hessen †                             500,000        10              100       11         50,000          25,000
 * Quantities in metric tons
 † Figures for Spring 1992
 ‡ Statistics not available for former East German (New German) states
 § Excluding Rhineland Palatinate figure in average, due to the higher proportion of paper and trade wastes

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   Table 1: Current Source Separated (Bio-waste) Collection and Composting Programs
               (Continued)in the Federal Republic of Germany (Old States)
 GERMAN STATE                                              CURRENT (Aug 1991)
                                   Residents      Per-      Bio-waste        Sites   Bio-waste        Compost
                                    served        cent     per resident               quantity        Quantity
                                                  (%)      (avg. kg/yr)               (t/yr) *         (t/yr) *
 Lower Saxony                         205,500        2.8              92       11         19,000              9,000
 Schleswig-Holstein                    81,600        3.1              78         4          6,350             3,320
 North Rhine-Westphalia               921,400        5.5             101       16         93,480          43,100
 Rhineland Palatinate                 233,600        6.2             176         7        41,000          23,840
 Baden-Würtemberg                     322,400        3.3              81       12         25,980          12,970
 Bavaria                              444,300          4              79       23         34,950          16,710
 Berlin                                32,000        1.5              47         1          1,500              750
 Hamburg                               11,500        0.7             110         1          1,270              635
 Bremen                                35,000        5.3             113         1          3,950             1,980
 TOTAL (western states -            2,787,300        4.5       avg. 89   §     87        277,480         137,185
 former West Germany) ‡
 * Quantities in metric tons
 † Figures for Spring 1992
 ‡ Statistics not available for former East German (New German) states
 § Excluding Rhineland Palatinate figure in average, due to the higher proportion of paper and trade wastes

Table 1 indicates that in1991 ca. 280,000 tons of source separated bio-wastes were composted at
about 90 compost sites in Germany, or double the amount from five years earlier [Fricke,1986]. In
the 1990's, a ten-fold increase is planned over the 1991 figures, to a total of 2.8 million tons of
bio-wastes handled and 1.3 million tons of compost produced (see Tables 1 and 2). The rate of
residential participation is set to increase from 4.5% in 1991 to 46% by the end of the decade,
with some areas intending to meet their targets already earlier. Collection efficiency and a high
level of quality standards are considered to be key to eventual public acceptance. Failure to
achieve a high-quality standard in advance of the developments could mean poor acceptance on
the part of the public [AKR, 1992].
4. MSW Quality Considerations
A wide variety of MSW operations were developed in Europe in the last 3 decades. Based on
these experiences and current research reflected in European publications, it is no presently con-
sidered to be effective or economical to separate contaminants back out of the waste stream once

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they have been mixed with the other fractions. Most of the early MSW composting facilities in
Europe have consequently been closed or converted to plants for handling source separated mate-
rials. One of the most significant fallacies identified in the early MSW procedures was the pre-
grinding of mixed waste. Pre-grinding allows contaminants to become mixed with fine fractions,
preventing later separation [Bidlingmeier, 1990; Freund, 1993]. This papers examines some rep-
resentative research comparing contaminant levels in mixed solid waste, wet waste, separated
garden wastes and 'bio-wastes'.
While German researchers have found that many contaminants in composts can be significantly
reduced through source separation of wastes, they have found that some contaminants are ubiqui-
tous in the environment. They are consequently difficult to eliminate from any waste stream;
even if organic wastes are source separated they will show up in the compost products. A variety
of analytical methods have been applied to trace the sources of chemicals including dioxins,
furans, PAH and PCB [Krauss, 1992; Anon., 1992]. This report outlines several of the research
Another aspect of waste contamination examined quite extensively in just the past few years is
that of toxic organic by-products and pathogens common to the organic waste stream, including
food industry, kitchen, yard and agricultural by-products[ Strauch, 1992; Lukassowitz, 1992].
Chemical compounds or microorganisms may either already be present in the material or arise
during the composting process. It is particularly in this area that a considerable amount of
research has been done lately in Germany looking into the effects of composting and the neces-
sary criteria to be met for safe and effective handling of the wastes involved.
Seen again in the context of the general waste problems in Germany, whether with the reduced
landfill space or the issue of pollution arising from the production, handling and disposal of the
various materials, it has been essential for Germany to thoroughly examine the questions of con-
taminants and hygiene in biological wastes and composts: with organic wastes representing a sig-
nificant portion of the total household waste stream (30-50%, depending on whether or not paper
is included), whether or not a compost product is safe and usable, without question, is a critical
point. Otherwise, composting could not be an integral part of their longer term waste handling
strategies. Hence, although most of the research has been carried out by institutes, universities and
industrial associations, much of it has been funded partly or wholly by regional or national gov-
ernment bodies. The research findings from these groups are then used as the basis for govern-
mental discussions, standard-making and laws.
4.1 Background Levels of Pathogens, Metals ands Organic Contaminants
The nature and source of contaminants in MSW and other composts must be properly appreciated
[Kehres, 1990]. Several researchers [Fricke, 1991; Kehres, 1990; Kraus, 1992; Kassel notes,

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1992] have emphasized the importance of taking background levels of contaminants into consid-
eration when evaluating composts and composting processes. Standards should not be adopted
that prevent compost materials from achieving markets if the source of contamination is unavoid-
able or natural. For example, at the 1992 European Waste Forum [Kassel, 1992], Kraus and
Strauch noted that EC limits being considered for certain contaminants could not even be met in
some commonplace materials in the home, such as certain foods and household dust, the latter of
which can contain high levels of both metals and organic chemical contaminants [Kraus, 1992].
A German Federal Health Office press release in 1991 [Anon., 1991] popularized concern about
the existence of the fungus, Aspergillus fumigatus, in composts. Subsequent scientific studies
documented the widespread nature of Aspergillus fumigatus in outdoor and indoor environments.
The fungi is commonly found in soils as well as in potting mixes for house-plants. Analysis of the
data suggested ubiquitous exposure risks at levels the same if not higher than those attributable to
compost sites [Strauch, 1992; Lukassowitz, 1992; Assman, 1992; Haertel, 1993; Jager, 1993].
Hygienic considerations played into the design of bio-bin containers and household compostable
bags for food collection [Kowald, 1989, 1991].
Background levels of heavy metals and organic chemical contaminants are often found in the dust
fraction, carried by winds and spread ubiquitously throughout the environment [Kassel, 1992].
Household dust, particulary vacuum-bag dust, an important component of MSW, is of particular
concern, as it carries very high levels of contaminants. Rainwater and groundwater are further
sources of background levels of some contaminants. Finally, a geologic relationship has been
noted by Fricke in that variations in background metal levels are influenced by the underlying
rock types [Fricke, 1991]. Composts from raw materials from regions with basalt formations
exhibited higher levels of chrome and nickel.
A considerable amount of research was done in the 1970's and 1980's in Germany and Europe in
general on contaminants and pathogens in sewage sludge, with some of the results being applica-
ble to composting [Strauch, 1989]. Sewage sludge is a well documented example of a waste mate-
rial with varying levels of contaminants across all three categories of pathogens, heavy metals and
various organic chemicals such as PCB's, PAH's, solvents and dioxin, with industry being the
major source of metals and organic contaminants. Because of the common practice of significant
amounts of sewage sludge being applied to agricultural land, there has been a coordinated Euro-
pean Community research program since 1971 to investigate the effects of metal and other chem-
ical accumulations in the soil as well as handling techniques for pathogen control. Many of the
results from this research were initially adapted to composts for process quality control and land
application recommendations based on contaminant levels and assessments of various quality cri-
teria [LAGA, 1984; Bidlingmeier, 1992], with revisions for the more specific characteristics of

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        bio-waste composts only at present being carried out [Mach, 19932,; Dittmer, 1993].
        5. Heavy Metals
        5.1 Environmental Levels
        European research has found higher levels of heavy metals in soils and composts from regions of
        heavy industrial activity [Fricke, 1991]. No significant generalized differences could be found on
        average values between composts from rural areas and those from city areas; it depended far
        rather on the specific metals and specific industrial regions involved. Thus, composts from the
        industrial North Rhine-Westphalia region showed significantly higher lead levels. One area in this
        region had soil lead levels of 2000 mg/kg. In composts analyzed, those from this region had the
        highest average levels of lead (from source separated materials). While the same region also had
        higher cadmium and zinc levels in composts, it had lower chromium nickel, copper and mercury
        than some other areas. Lead, cadmium and zinc are the metals which most often (50-60% of com-
        posts) go above quality limits set by the German RAL standards for composts (see section later).
        Alex Pfirter of ANS in Switzerland, speaking at the 1992 Kassel conference, related how levels of
        lead in composts went down after the introduction of unleaded fuel [Kassel, 1992].
        Levels of metals in 'Bio-Composts' in Germany are shown in Table 4 [Fricke, 1991], taken from
        490 samples, compared with garden soil levels determined in a survey carried out in Bavaria com-
        missioned by the Ministry of Regional Development and Environment. The bio-composts are
        made largely from source separated kitchen and yard waste materials. The metal levels in the
        composts are comparable with observed soil background levels. It is now common practice in
        Germany to adjust heavy metal analysis results to a 30% OM level to allow more reliable compar-
        isons between different composts;- the metal level varies in proportion to the organic matter lev-
        els when total dry matter is considered [Bidlingmaier, 1992; RAL, 1992; Kehres, 1990; Fricke,

                       Table 2: Metal Levels in ‘Bio-Composts’ and Garden Top-Soil
Graph                                          Bio-composts    Bio-composts          Garden
                      Heavy Metal               at 30% OM      at original OM        top-soil
                                                (mg/kg dm)      (mg/kg dm)         (mg/kg dm)
                      lead (Pb)                        83.07               77.64           77
                      cadmium (Cd)                      0.84                0.78          0.45
                      chromium (Cr)                    35.83               33.73           38
                      copper (Cu)                      46.76               43.24           37
                      nickel (Ni)                      20.48               19.13           21
                      zinc (Zn)                        249.6              232.82          179

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               Table 2: Metal Levels in ‘Bio-Composts’ and Garden Top-Soil

                                      Bio-composts      Bio-composts        Garden
               Heavy Metal             at 30% OM        at original OM      top-soil
                                       (mg/kg dm)        (mg/kg dm)       (mg/kg dm)
               mercury (Hg)                     0.38              0.33            0.36

It is to be emphasized that the levels presented in Table 4 above are average, signifying that some
may be significantly higher, or lower. Another study of 200 bio-waste and yard waste composts
showed, for instance, average lead levels of 62 mg/kg (dry matter); the range, however, was
between <1 and 1,103 mg/kg [Crössmann, 1991]. The causes for this variation can be understood
when contrasted with soil lead levels of 2,000 mg/kg found in one region mentioned above.
5.2 Heavy Metal Levels in MSW Composts - Experiments with Metal Separation Technologies
First research efforts in the later 1970's and 1980's towards a solution for reducing the high heavy
metal levels in MSW composts was in metal separation technologies, with generally discouraging
results: either the technology was not effective or the cost s were too prohibitive [Kraus, 1992;
Hangen, 1991; Wuttke, 1992; Strauch, Mar89]. It was not a matter of simply removing foreign
object, as in plastics, tins, etc. A complication for the removal technologies was that the predomi-
nance of contaminants was in the fines fraction of the compost, and hence could not be physically
removed [Kraus, 1992].
The Bad Kreuznach composting facility, built in 1958 to handle large amounts of municipal
wastes, provides a representative case history. It provided compost in its early days to vineyards
in the region, which could no longer receive enough manure for maintaining soil quality. With the
concern in the 1970's about contaminants, the facility faced closure, but was taken over by
another firm as an experimental plant. The early 1980's saw the first source separation composting
experiments in other regions, and it was decided that the facility be rebuilt to eventually be able to
handle such materials. In the meanwhile they experimented with removal of compost contami-
nants, including heavy metals, through technical means. These trials were abandoned in 1989
after “many painful experiences”, according to Hangen [Hangen, 1991]. In 1989 they started their
own pilot scheme for source separation, with very positive results. They now take separated
kitchen, food industry (including fruit slurry), yard and paper wastes (including paper sludge)
from the whole city. Handling over 50,000 metric tons/annum, they are one of the largest facilities
in Germany. Lead levels have been reduced on average to one-eighth of the MSW compost levels
(70 mg/kg compared with 573 mg/kg from earlier sample averages), with cadmium one-fifth and
zinc one-quarter of earlier levels.

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5.3 Heavy Metals in 'Bio-Composts' from Source Separated Materials
The positive effect of source separation on reduced heavy metal as well as organic chemical con-
taminants levels in composts from numerous trials has been quite pronounced [Jager, 1991;
Funke, 1992; Kehres, 1990; Kraus, 1992; Fricke, 1991; Kranert, 1991]. Owing to these experi-
ences, one can quite definitively speak of the demise of MSW plants in Germany. At present
there are only four MSW plants remaining in the country and three of these are due to close, as
noted earlier.
It would be misleading, however, to suggest that source separation has solved the problem of con-
taminants in composts. Although significantly lower, 50-60% of bio-waste composts, as men-
tioned above, still are above metal limits set by RAL, though often marginally. The RAL metal
limits, themselves, stem from earlier research on sewage sludge application rates in relation to
metal levels and other contaminants. Soil loading rates were worked out based on a maximum
acceptable build-up over a 10 year period, which translated into maximum sludge application
rates per year depending on the particular contaminant levels. Maximum contaminant levels
allowable for composts were adjusted to allow for a higher desired application rate of composts in
comparison to sludges, resulting in the Blue Angel and RAL Compost Quality levels for metals.
Yard waste compost, according to German research findings, generally have slightly lower levels
of metals than combined yard and kitchen wastes; bio-waste composts with paper added tend to
have somewhat higher levels. MSW composts have the highest levels, with wet-waste compost
just under MSW levels. Comparative metal levels from representative sites are shown in Table 5
below, adjusted for 30% organic metal level. All composts tend to have higher levels during the
winter months, particularly in December and January [Krauss; Kranert].
Beside background levels, there are some further point source contaminants that have been found
to contribute to metal levels in bio-wastes. Foreign object levels in source separated organic mate-
rials for composts in Germany are usually at a very low level - an average of 2%, according to
Fricke [Fricke, 1991], and directly proportional to the publicity and general educational efforts
undertaken. Even this smaller amount, however, can in some circumstances contribute still to
metal levels. Certain types of paper, if this is included, can have higher levels [Bidlingmaier,
1990]. Depending on the coatings, inks and printing processes used, higher zinc and copper levels
have been found in composts using paper, in some cases bringing levels over the RAL limits.
Metal levels in printed matter are, however, being reduced through new materials developed, and
it is foreseen that the paper fraction in the future will be able to be used without concern for these
contaminants [Fricke et al, 1991].

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           Table 3: Average Heavy Metal Content of Different Types of Composts†

                Bio-compost Bio-compost         Yard waste         Wet-waste     MSW
 Metal                       with paper          compost           compost      compost
                                                                                            for composts
                (mg/kg dm) (mg/kg dm)           (mg/kg dm)        (mg/kg dm)   (mg/kg dm)
                                                                                            (mg/kg dm)‡
 lead                  83.07           116.2               63.1          705          596           150
 cadmium                 0.84           0.96               0.72         4.08         6.39            1.5
 chromium              35.83            39.8           28.44             113         82.9           100
 copper                46.76            76.2           34.52           357.8          318           100
 nickel                20.48            21.4           18.56            47.1         52.1            50
 zinc                  249.6           350.3          176.92            1334         1823           400
 mercury                 0.38           0.54               0.28         1.62         2.79            1.0
 † Levels adjusted to 30% Organic Matter (OM) level
 ‡ RAL limits given for after adjustment to 30% OM level

Investigations into the cause for higher levels during the mid-winter months revealed that Christ-
mas related items, including wrapping paper and remains of tree decorations (tinsel!), were often
to blame for a significant part of it [Kranert, 1991;Krauss]. Wine bottle tops, making their way
accidentally into source materials, as well as lead castings from traditional German New Year's
Eve games, have been found to contribute significant levels of lead to bio-waste composts, in one
study as much as 80-90% of total compost lead levels. Composts from experiments in which dis-
posable diapers were added to bio-wastes showed elevated zinc levels [Obermeier, 1991], though
still usually within limits. This was due to the presence of zinc creams used commonly in t he
treatment of baby rashes.
Occasionally, equipment involved in composting has been found to contribute to heavy metal lev-
els in the composts, with for instance nickel and chrome from parts of the shredding and process-
ing equipment [Kranert, 1991].
Thus some of the findings indicate that it is a mistake to always contribute heavy metal levels to
industrial sources: some sources can be found very close to home. Continuing emphasis on vigor-
ous separation of the original materials as well as broad scale efforts at tackling pollution levels
will eventually have their positive effects on contaminant levels in composts.
6. Organic Chemical Contaminants in Composts
This section looks at the category of organic chemical contaminants such as PAH, PCB, PCP,

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          dioxin, etc., both in source materials and compost products. Research reports from Germany on
          many types of chemicals found in wastes and composts could be looked at which pose potential
          questions for plant and human health. Those which are looked at here are currently occupying the
          main attention of researchers and composters.
          6.1 Toxic Organic Chemicals in Composts
          Early research on contaminants, including toxic organic chemicals, in fertilizers and composts
          concentrated on sewage sludge and sewage sludge products, as noted in the previous sections
          [Strauch, 1989]. A great variety of chemicals have been found in sewage, including PCB's,
          dioxin, solvents, insecticides, herbicides, petroleum products, and detergents. Since many of these
          compounds are widely distributed in the environment, and are used in households, municipalities
          and institutions, it is not surprising that appreciable contamination is seen in bio-waste composts.
          As noted in the section in which metal levels in MSW compost are discussed, general contami-
          nant levels in compost products have been significantly reduced through source separation of
          materials; this includes chemical contaminants as well [Fricke; Krauss; Kehres; Jager, 1991].
          Similar to metal levels, yard waste compost exhibits slightly lower levels than bio-waste (food
          and yard waste); 'wet waste' composts show significantly higher levels than both yard and bio-
          waste composts, but lower than MSW. These relative levels are true for most chemical contami-
          nants investigated by several researchers; PCB, PAH and dioxin/furan levels found by Fricke et.
          al. [Fricke] are given in Table 7 below. The findings are similar to those reported by Kehres and

                        Table 4: Organic Contaminants in Composts from Different Sources

           Element                    Bio-        Yard waste       Wet waste        MSW             Rural               Urban
                                    compost        compost         compost         compost       bio-compost         bio-compost
           PCB† ng/g dm                259.66            177.5             938           1493          279.38a           281.57a
           PAH ng/g dm                   1707             1560           3370            4412           284.9a         3421.25b

           dioxin/furan                 12.07            10.58              50            103           10.15a            12.68a
PAH,         ng TE/kg dm§
PCB and
PCDD       † Includes all isomers of PCB’s
Graphs     ‡ Includes 6 forms of PAH’s which are regulated in the German Drinking Water Ordinance (Trinkwasserverord-
           nung - TVO)
           §TE= Toxicity Equivalents, as per German Federal Health Office standards and International Units
           ab - letters in the same row which do not differ are not statistically significantly different @ p=0.05
           Source: Fricke, revised by Woods End Research Laboratory, Inc.

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From figures shown for Bio-waste compost, the question is again raised about background levels
and the sources that are contributing to them. Fricke et al found that PAH levels in composts were
significantly influenced by the geographical location of source materials, whereas PCB's and
dioxin/furan were not: levels of PAH's in urban area composts were seven times higher than those
from rural areas, while PCB and dioxin/furan levels were similar (see Table 7 under 'rural' and
'urban' composts). This confirms that current industrial activities are influencing the PAH levels,
which arise from incomplete combustion processes, with the other chemicals tested being more
ubiquitous. Kraus found that dust is the primary carrier of organic contaminants such as PCB,
PCP, PAH, dioxin and furan, which can then be air-borne and widely distributed in the environ-
ment. Household dust is included in this, with high levels of contaminants found, originating both
from general environmental dust as well as more specific household activities, e.g. PCP's from
carpets, treated wood, textiles, etc. [Krauss]. Because of this, vacuum cleaner bags are not
allowed in bio-waste collections.
While specific standards and limits have not been set for levels of chemical contaminants in com-
posts, it is not viewed as a problem by German researchers and composters if separation proce-
dures are adhered to for source materials [Fricke & Turk, 1991]. Although there are still some
persistent levels in Bio-waste composts (from source separated food and /or yard wastes), these
are below generally accepted limits. Some further reduction is possible through improved separa-
tion, but beyond this broader environmental measures would be required.
6.2 Compostability of Organic Chemical Contaminants
Whether or not organic chemical compounds can be broken down in composts depends on many
factors including concentration of compound, substrate availability and adaptability of bio-flora
to the environmental conditions. The difficulty of bio-degradation products must be acknowl-
edged. Jager [Jager et al, 1991] describes pathways of breakdown of organic and synthetic com-
pounds in compost piles. Some organic chemicals can only be broken down under aerobic
conditions, due to the particular chemistry of oxidation necessary for them: some chemical bonds
are only broken in the presence of oxygen, e.g. saturated hydrocarbons. TNT can be decomposed
in composts by either aerobic or anaerobic conditions [THAMA, 1992]. Oil is given by Jager as
an example o f a compound which is not easily broken down under anaerobic conditions.
Bacteria can play a major role in the break-down of organic chemicals. The important factors for
breakdown of compounds by bacteria are related to conditions for the microorganisms: growth
conditions, inhibiting factors or compounds for microorganisms, and nourishment of microbes.
Some bacteria are more adaptable than others to the break-down of synthetic compounds. Jager
gives the examples of Pseudomonas, which are particularly adaptable. Within the genus, there is a
specialization of specific types for various categories of compounds including P. putida for phe-

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nols and P. chrysosiporium for PCB, PAH and dioxin. Most of these bacteria are naturally present
in biological waste materials; some bioremediation processes will add inoculants which contain
higher levels of a specific bacteria for increasing the desired break-down level, but inoculum
approaches have proven unreliable [ENSR, 1990]. Inocula with proven degradative potential in
the laboratory often loose this ability once put into the field.
Fricke [Fricke, 1991] reviews composting research trials in Witzenhausen where the break-
down of organic contaminants was tracked. The degree of decomposition was shown to be depen-
dent on both the specific compound as well as the composting conditions. Hydrocarbons, includ-
ing petroleum, were significantly decomposed, PAH's were decomposed to a certain extent, and
PCB's were the least decomposed. The degree of PCB breakdown was related to the chlorination:
low chlorinated PCB's decomposed more, with a range of 15-74%. PAH's in these experiments
showed a break-down rate of 49-65%. Maine trials of PAH breakdown in MSW composts gave
promising results if the PAH’s were not high initially [Brinton & Collinson, 1991].
Other less complex organic compounds have been shown to have a very high decomposition rate
in composting. Antibiotics, for instance, which can be found at significant levels in animal excreta
in farm operations (90-100% of antibiotics can be excreted), wa s found to be eliminated at a rate
of 80% through composting [Vogtmann, 1978]. If the antibiotics are not eliminated, they can be
taken up into plants when the manure is spread onto fields. Nevertheless, factors in compost
which encourage biological degradation of contaminants should not be used to obscur the signifi-
cance of source reduction of chemicals. The German experience proves that compost of high
quality can be produced provided suitable standards are in place.

7. Acknowledgments
The authors would like to greatfully acknowledge the contributions of Peter Krauss, Klaus
Wiemer , Dieter Strauch of Germany and to the Members and President of Business in The Envi-
ronment (London) which originally inspired the Woods End evaluation of German recycling and


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8. Authors Addresses
William Brinton1 and Jonathan Collinson
Woods End Research Laboratory
Box 1850, Old Rome Road
Mt Vernon Maine 04352

Richard B. Brinton
Woods End Research Laboratory, Ltd.
PO Box 79, Stroud, Glouc. ENGLAND GL5 3PU


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